Hand trucks are universally used as a means to carry small-sized heavy loads amenable to their use. Typically, a hand truck is intended for use by an individual, rather than team of persons. The truck is typically equipped with a set of two wheels, a single handle, and includes a pair of side rails with a bottom plate extending outwardly from the wheels as tongue and in a generally perpendicular relation to the side rails. The handle portion is generally integrally attached at the topmost portion of the side rails. In use, the bottom plate is slipped under a load and the load is tilted so as to bear upon both the bottom plate and the side rails. The hand truck can then be easily steered by the user. However, the maneuverability of the load is largely a function of the ease with which a two-wheeled truck can be pivoted or swivelled on its wheels, and this maneuverability also requires that the load pivot (or more accurately, rotate) about the wheel and toward the user, who then bears some of the load.
Thus, a disadvantage of using hand trucks rests not so much in their own load-bearing limitations, but in the load-bearing limitations of the users, which is to say that some loads are simply too heavy or too unwieldy for an individual to move with the hand truck. This limitation can be considerably extended if the load-bearing requirements of the user are removed or substantially removed.
To this end, some hand trucks have been equipped with permanent third wheels, or rear stabilizers. Exemplary patents include the following:
U.S. Pat. No. 4,033,595, to Mauch, discloses a hand truck having an auxiliary frame on its main frame. The auxiliary frame is adapted for adjustable mounting of a third wheel. The auxiliary frame is provided with a radius rod with an inner end pivotally attached to the lower end of the main frame. When the auxiliary frame is pulled outwardly it locks on the end of the radius rod. This enables the operator to place his foot on the cross-member of the auxiliary frame to assist in tilting the load about the main support wheels. In addition, the third wheel is spring loaded to extend below the auxiliary frame and its extension is made adjustable by a foot-operated lever; when depressed it frees the spring loaded third wheel permitting it to extend downwardly.
U.S. Pat. No. 5,947,491 to Meier, teaches a hand truck with brake elements actuable and releasable by foot operation of the user, for setting and releasing the brake. The brake may also be actuated by hand operation, but the hand operation will not set the brake. The brake elements include plates movable against a wheel to prevent the wheel from moving backwards or in the rear position. The apparatus of the present invention also includes a retractable pair of stabilizer wheels disposed on a stabilizer frame and movable to a down or use position and to an up and storage position, as desired. The stabilizer frame is secured to the main frame of the dolly and pivots thereon between a stowed position and a down, use position.
U.S. Pat. No. 6,328,319 to Stahler, Sr., et al, shows a hand truck convertible into a cart having an elevated tabletop surface. The hand truck has a primary frame with rotatably mounted wheels. The hand truck has at least one additional wheel adapted to allow the hand truck to be used as a cart. The primary frame is generally parallel to a supporting surface while the hand truck is being used as a cart. The improvement to the hand truck includes a plate movably attached to the primary frame and movable between a first position, generally parallel to and contacting the primary frame, and a second position, generally parallel to and spaced apart from the primary frame, forming the tabletop surface.
U.S. Pat. No. 4,630,837, to Kazmark, discloses a hand truck with an auxiliary wheel which can be moved between a storage position and a supporting position. When the auxiliary wheel is in the storage position, the cart can be used as a two-wheeled cart. When the auxiliary wheel is in the supporting position, the cart is supported on a three point stance and is self-supporting.
The foregoing patents notwithstanding, there is as of this date, and to the knowledge of the present inventors, no known auxiliary wheel set adapted for aftermarket installation on hand trucks of varying sizes to provide for rear stabilization and load support. It would be desirable, therefore, to provide such an apparatus with all the appurtenant objects and advantages. Accordingly, the foregoing patents reflect the current state of the art of which the present inventors are aware. Reference to, and discussion of, these patents is intended to aid in discharging Applicants' acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the above-indicated patents disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein.